In telecommunications systems, such as the second generation (2G) mobile network, capacity restraints have resulted in the decline in average revenue per user thereby encouraging mobile operators to consider upgrading their network and services to a third generation (3G) network. However, the relative slow consumer response to data services, on top of the burst in the Internet bubble, have contributed to the more careful capital expenditure and the subsequent deferral of 3G deployment. Most major mobile operators now are more relying on using an intermediate 2.5G network technology, such as General Packet Radio Service (GPRS), Enhanced Data for GSM Evolution (EDGE), or Code Division Multiple Access (CDMA) Radio Transmission Technology (1xRTT) to provide data services.
The delay in building 3G networks and the reluctance for putting in more radio transmitters make it desirable to find ways to use the limited radio resource more efficiently. At the same time, mobile consumers are demanding more services and higher service quality. Operators must also be careful to avoid creating negative user experiences like those associated with the unsuccessful Wireless Access Protocol (“WAP”). All these challenges may lead to an opportunity for innovative solutions for optimizing the 2.5G network.
The scarcity in Radio Access Network (RAN) resources can seriously affect the quality of data service in wireless networks and negatively influence its acceptance. Wireless 2.5G data networks are basically overlay radio networks. Sharing of radio resource is desirable as the same radio equipment can be used both for voice and data, allowing the introduction of wireless data services without large capital expenditure. However, to meet a “good” voice quality, it can be shown that on the average, half of a Time Division Multiple Access (TDMA) time slot in a Global System for Mobile Communications (GSM) mobile system will be used by voice. In GSM systems, voice normally preempts data, therefore, less than half of the TDMA slots can be used for carrying data. This situation will be worse during peak voice usage hours.
In the mobile environment, the largest performance bottleneck occurs at the radio access network (RAN). In deferring investing large capital expenditure to upgrade the RAN and increase radio capacity, it is unavoidable that congestion will happen at the RAN. When that happens, it would be desirable to provide differential treatment for certain customer's traffic compared to others. Differentiated service suggests providing more network resource to the premium (or preferred) customer's sessions, or giving higher priority to certain traffic when degradation is unavoidable. A Quality of Service (QoS) scheme is needed to provide differentiated services. In 2.5G wireless networks, however, there is no explicit QoS control in the radio network. In 3G/UMTS networks QoS will be partially addressed, but large scale 3G deployment is not expected for several years
Most service providers are motivated to provide differentiated services, as certain customers, such as corporate customers, are expected to generate a larger return on investment than non-corporate customers. Providing differentiated services is more challenging in the wireless environment than in its wireline counterpart. In additional to the scarcity in radio resource, locating mobile customers, and tracing sessions and their network resources is a fundamental challenge. Without this information, it will be very difficult to differentially control and allocate network resources with respect to a special set of premium customers.
The 3G UMTS (3rd Generation Universal Mobile Telecommunication System) is a proposed architecture that supports end-to-end Quality of Service (QoS). It is based on Internet Protocol (IP) QoS and a QoS policy interface (Go) defined between the Gateway GPRS Support Node (GGSN) and a new function called Policy Control Function (PCF). The PCF is part of a module called P-CSCF (Policy—Call State Control Function), which is part of the IMS (IP based Multimedia Service Platform) architecture.
The UMTS QoS support is based on IP QoS mechanisms including DiffServ, Intserv, Resource Reservation Protocol (RSVP), and QoS Policy management via the Common Open Policy Service (COPS) protocol from the Internet Engineering Task Force (IETF). In the current UMTS system, the higher level QoS request is mapped into policies at the PCF module. Policy is conveyed between the PCF and the IP BS (Bearer Service) manager located in the GGSN and the mobile terminal. The IP BS QoS requirement is further mapped into UMTS QoS requirement at the Policy Decision Point (PDP) Context level. Support of QoS policy is via the PDPContext setup. During the PDPContext setup, the GGSN will request an authorization from the PCF module. After authorization, the PCF sends back a decision to the GGSN where the policy is enforced. The GGSN then generates a “Create PDP” Response back to the SGSN, which then sends an “Activate PDP” message to the mobile station to complete the PDP set up. It is also possible to change the QoS Policy after the initial set up. This can be initiated by either the MS or the PCF.
QoS control in 3G UMTS is driven by the IMS architecture. UMTS has added many QoS capabilities into the network. It relies mainly on IP QoS and a QoS Policy Decision Point (PDP). It has moved the Admission Control function outside the SGSN (in release 99) to be now located in the PCF (Release 5). This provides a very flexible and powerful architecture with respect to admission control, which was not accessible to OSS in 2.5G systems.
Providing UMTS QoS capabilities is expected to be an evolutionary process. However, early form of these capabilities can be implemented with a simple GGSN and a Policy Decision Point architecture, not necessary with a full-fledged Go interface. Thus, it is important to be able to migrate from a strategy in which many QoS capabilities can be provided in the near term (1-2 years) with an evolution towards the ultimate UMTS QoS capability.
The current problems to be addressed are the radio resource scarcity and service differentiation issues. In 2.5G wireless networks, there is no explicit QoS control in the radio network. Although 3G/UMTS network provides a lot more QoS capabilities, 3G deployment is not expected in large scale for at least three years. However, even the current 3GPP UMTS Release 5 does not adequately address the quality of service needs as there is still no QoS in the RAN even in 3G.
It has been generally concluded that one effective way to deal with the scarcity in radio resource is via digital compression of the source content, or by using software accelerator (another term for compression). This is particularly useful as RAN congestion is expected to happen mostly in the downlink (from server to MS direction) for most data applications. Another reason for compression is that mobile terminals come in all sizes and many of them do not require a full resolution display. This provides much flexibility and an opportunity for significantly reducing the data rate requirement for many mobile terminals. Compression alone, however, will not be enough to save the bandwidth necessary to provide the various services desired by customers.
With regard to the QoS issue in mobile networks, many QoS control mechanisms have been proposed in the past, including Differentiated Services (DiffServ), Integrated Services (IntServ) via RSVP, Multi-Protocol Label Switching (MPLS) and virtual circuit technologies such as Frame Relay (FR) and Asynchronous Transfer Mode (ATM). Whereas each of these technologies has its own merits and shortfalls, mobile operators have converged on IP as the fundamental protocol that is considered most ubiquitous and is the focal point for relating customer session service requirements to lower layer network implementation of QoS. Between the two QoS mechanisms available in IP, DiffServ has come out to be the more desirable mechanism over IntServ. The Intserv model requires state information for every IP flow or session in a router, which causes scalability problem that renders its implementation impractical. DiffServ, on the other hand, only requires each router to handle a small set of QoS classes and is thus considered to be a good compromise between the per-flow Intserv and regular “best of effort” service
IP DiffServ is a common mechanism for providing quality of service in IP networks. DiffServ requires each IP router to handle a small set of QoS classes and prioritizes the traffic based on these classes. The DiffServ service classes are based on several header fields in IP packets: IP source and destination addresses, IP protocol field, IP port number, and DiffServ code points (DSCP) or IP precedence (Type of Service, TOS) bits. DiffServ can provide QoS control using traffic shaping/rate limitation, policy based routing, and packet dropping policy. DiffServ's decision-making and policy enforcement is performed at each router (each hop the packet traverses) based on information local to the router. In the case of 2.5G networks (e.g., GPRS), the last hop for a packet destined for a mobile host is the gateway between the wireless core network and the IP network (the GGSN, in the case of GPRS). However, congestion is most likely to occur in the Radio Access Network (RAN), which is not directly adjacent to the IP gateway. Thus, the gateway does not observe the congestion and cannot use DiffServ to address the congestion problem.
The Internet DiffServ architecture provides powerful mechanism for controlling QoS. However, there are a number of issues that warrant careful consideration before it can be used successfully for mobile networks. The DiffServ architecture focuses around a local device, such as a router or bandwidth broker as a key QoS policy Enforcer. However, in many scenarios, the triggering events, such as congestion in the RAN, are remote from the enforcement point. It is important that QoS policy decision be made properly taking into account the relationship between the cause (congestion point) and the cure (PEP). The “cause and effect” of QoS policy and enforcement is hard to verify and a separate OSS structure is required to convince providers that they are getting what was promised. The linkage between IP QoS and customer and service level SLA is not defined and the mapping is ad-hoc and complicated. This requires operators to “understand” what is the right QoS policy and how should the policy be coordinated among multiple QoS policy enforcement points so that end-to-end QoS goals are satisfied.
Therefore, it would be desirable to have a QoS policy enforcement and traffic optimization system that overcomes the shortfalls of DiffServ and Intserv.
Furthermore, it would be desirable to have a system and method that enables optimal use of RAN resources.
Additionally, it would also be desirable to have a method and system that is able to provide for fine-grained QoS in a mobile network thereby providing quality of service on a user-by-user basis without having the overhead problems created by a session-by-session system such as Intserv.
Furthermore, it would be desirable to have a method and system capable of implementing policy based QoS to meet various user demand.
Also, it is desirable to have a method and system enables controlling, shaping, and optimization of traffic at a point in the network away from the point of RAN congestion.
Finally, it would be desirable to have a method and system capable of supporting a wide-range of different access networks.